Laser gain media are used in lasers. For example, both thulium-doped and holmium-doped lasers are important laser sources because they are considered “eyesafe,” i.e., in the 2 μm spectral region, and have applications in remote sensing, and medical and military technology. Thulium has several favorable properties with respect to laser diode pumping, such as a strong absorption band at a diode emission wavelength around 785 nm and an efficient cross-relaxation process yielding two ions in the upper laser level per absorbed pump photon.
Some Tm—Ho lasers are comprised of two separate laser systems combined in series. However, the cost, bulk and complexity of such systems are relatively high, and flexibility of design options to tailor for different applications is limited. Other Tm—Ho lasers are formed of a co-doped holmium/thulium laser gain element where the co-doped laser gain element behaves as a single region.
However, it has been a challenge to obtain laser radiation of both good beam quality and high power.